1. Field of the Invention
The invention relates to a method for supplying analysis apparatuses and liquid-handling systems with liquids that are kept available in storage tanks.
The invention also relates to a device for carrying out such a method.
2. Description of Related Art
Examples of analysis apparatuses that work with liquids include column chromatographs, whose mode of operation is based on the method of chromatography. The chromatography method is widespread, particularly in chemistry, and allows the separation of substance mixtures through the differential partitioning of their individual constituents between a stationary phase and a mobile phase. The chromatography method is employed, for instance, to isolate and purify substances as well as to analyze the composition of substance mixtures in terms of their contents and quantities.
A prerequisite for carrying out the chromatography method is the presence of a stationary phase and a mobile phase. The stationary phase interacts with the individual constituents of the substance mixture, resulting in a separation of the substance mixture into its individual constituents. For this reason, the term separation segment is often employed for the stationary phase that does not move. The substance mixture that is to be processed, however, is placed into the mobile phase which, for purposes of the separation, moves through the stationary phase together with the substance mixture.
In column chromatography, the stationary phase is normally solid and is also referred to as the sorbent or sorption agent. Known sorbents are, for instance, silica gels or polymers. The mobile phase, in contrast, is normally liquid in column chromatography and is also referred to as the eluent or elution agent. Different solvents are used as eluents, depending on the substance mixtures that are to be analyzed.
Eluents are usually highly flammable and sometimes also toxic hazardous materials that, together with air, can form an explosive atmosphere, which is why they must be stored in safety cabinets so as to comply with the stipulations of the German Chemical Law. These safety cabinets ensure not only safe storage but also prevent vapors from escaping into the surroundings.
One of the most frequently employed special methods for column chromatography is high performance liquid chromatography (HPLC) as a form of liquid chromatography (LC). High performance liquid chromatography makes use of hollow tubes as separation or chromatography columns, which are filled with the stationary phase and through which the eluent moves as the mobile phase. The solution that flows out of the separation column after the separation is called the eluate, which is fed to a downstream detection system for analysis purposes.
A refinement of high performance liquid chromatography is ultra high performance liquid chromatography (UHPLC), which has a far better performance than high performance liquid chromatography and which likewise works with separation columns.
In order to separate a substance mixture into its individual constituents, in high performance liquid chromatography, the eluent is normally pumped through the separation column. Supply systems with HPLC pumps are known for this purpose. On the low-pressure side of these HPLC pumps, the eluent is taken from a storage tank that is normally arranged above the HPLC pumps, and, on the high-pressure side of the HPLC pumps, the eluent is then moved through the separation column. Towards this end, the eluent is kept available in the storage tank without being pressurized.
The familiar supply systems, however, have several drawbacks. On the one hand, with these supply systems, the storage of the eluent at times poses safety risks and potential health hazards for the operators while, on the other hand, only a limited amount of eluent is available in a storage tank due to restrictions on the maximum storage quantity permitted. As a result, however, autonomous and automated analysis operation employing high performance liquid chromatography is not possible.
For this reason, it is also a known procedure to connect two or more storage tanks to each other in order to attain an optimized supply. This, however, calls for the use of additional components such as, for instance, pumps, valves, sensors or fittings, all of which come into contact with the eluent. The eluting power of the eluent, however, increases the potential risk of contamination occurring in the eluent, which can possibly falsify or even invalidate the analysis results for the substance mixtures that are to be analyzed.